CVE-2026-4698

JIT miscompilation in the JavaScript Engine: JIT component

Severity Score

9.8

*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Attend

*SSVC

Descriptions

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability affects Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.

Miscompilación JIT en el motor JavaScript: Componente JIT. Esta vulnerabilidad afecta a Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149 y Thunderbird < 140.9.

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

This vulnerability allows remote attackers to execute arbitrary code on affected installations of Mozilla Firefox. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists within IonMonkey when optimizing JavaScript switch statements. The issue results from the lack of proper validation of user-supplied data, which can result in a type confusion condition. An attacker can leverage this vulnerability to execute code in the context of the current process.

*Credits: maxpl0it working with Trend Micro Zero Day Initiative,maxpl0it

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

* Common Vulnerability Scoring System

SSVC

Decision:Attend

Exploitation

None

Automatable

Yes

Tech. Impact

Total

* Organization's Worst-case Scenario

Timeline

2026-03-23 CVE Reserved
2026-03-24 CVE Published
2026-04-25 EPSS Updated
2026-05-07 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')

CAPEC

References (5)

URL	Tag	Source
https://www.mozilla.org/security/advisories/mfsa2026-23
https://www.mozilla.org/security/advisories/mfsa2026-24

URL	Date	SRC

URL	Date	SRC

URL	Date	SRC
https://www.mozilla.org/security/advisories/mfsa2026-20	2026-03-24
https://www.mozilla.org/security/advisories/mfsa2026-21	2026-03-24
https://www.mozilla.org/security/advisories/mfsa2026-22	2026-03-24

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Mozilla Search vendor "Mozilla"		Firefox Search vendor "Mozilla" for product "Firefox"				< 115.34.0 Search vendor "Mozilla" for product "Firefox" and version " < 115.34.0"		esr		Affected
Mozilla Search vendor "Mozilla"		Firefox Search vendor "Mozilla" for product "Firefox"				< 149.0 Search vendor "Mozilla" for product "Firefox" and version " < 149.0"		-		Affected
Mozilla Search vendor "Mozilla"		Firefox Search vendor "Mozilla" for product "Firefox"				>= 128.0 < 140.9.0 Search vendor "Mozilla" for product "Firefox" and version " >= 128.0 < 140.9.0"		esr		Affected